Conventionally, as shown in FIG. 1, a moving blade 1 of a low pressure turbine is composed of three assemblies: a lower part called the foot 10, an upper part called the heel 20 and a central part formed by the vane 30.
The foot 10 of the mobile blade 1 is composed of three functional elements:                a shank 11 making the connection between the vane and the foot 10;        a bulb 12 making the mechanical connection between the mobile blade and a turbine rotor disk;        spoilers 13 reducing leaks to maximise the efficiency of the low pressure turbine.        
The shank 11 is an important part of the foot 10 because it maintains the mechanical connection between the vane 30 and the foot 10 that is fixed to the rotor disk and is consequently the location at which there are high mechanical stresses.
Conventionally, mobile blades of the low pressure turbine have shanks that are approximately straight corresponding to the shape of the top part of the bulb (i.e. the top part of the dovetail).
However, such shanks cannot satisfy the required mechanical requirements in some geometric configurations, particularly in the presence of complex shaped vanes.
In such situations, curved shanks have been developed that have the same shape or more precisely the same profile as the vane so as to provide maximum overlap between the shank 11 and the vane 30 or more precisely between the profile of the cross-section of the shank 11 and the profile of the cross-section of the vane 30.
The development of this type of shank configuration has made stresses in this part of the blade uniform but has also contributed to increasing the mass of blades and consequently of the low pressure turbine. It will clearly be understood that an increase of a few grams in the mass of a mobile blade would have the consequence of increasing the mass of the entire turbine that comprises a plurality of stages, each stage being formed by several hundred mobile blades, by several kilograms.